Culture

Winter hardy to USDA Zones 9-11 where plants are best grown in deep, fertile, organically rich, humusy, consistently moist, well-drained soils in full sun to part shade. Soils should not be allowed to dry out. Vine needs a support structure upon which to grow to ensure foliage receives good exposure to sun. Plants can spread invasively by seed, underground tubers and bulbils (aerial tubers). To help prevent invasive spread, harvest tubers at the end of the growing season and replant each year plus remove and destroy bulbils that may appear. In tropical areas, plants go dormant for about three months at the end of the rainy season. In more temperate frost-free areas, plants lose foliage and go dormant in winter. Propagate by dividing tubers when dormant or from root cuttings in spring or by planting bulbils in spring. Where not winter hardy, this plant may be grown ornamentally in pots as an annual. Plants grow best in temperatures above 70 degrees F.

Noteworthy Characteristics

Dioscorea alata, commonly known as water yam or winged yam, is a fast-growing, twining, tuberous-rooted, herbaceous perennial vine of the yam family (Dioscoreaeae). It produces a large root crop of edible subterranean tubers (yams) which are an important starchy food source in many tropical to sub-tropical areas around the globe. This species is probably the most important and extensively cultivated of the edible yams, with significant cultivation occurring in the West Indies, West Africa, Southeast Asia and Central America.

Quadrangular purplish-winged stems (to 30’ or more) are clad with long-petioled, broad-ovate, bright green leaves (to 6-8” long) featuring 5-7 conspicuously sunken veins and cordate to arrowhead-shaped bases. Leaves are primarily opposite, but appear alternate near the base. Stems are herbaceous and not woody. Monoecious yellow-white flowers appear in pendant axillary racemes (male flowers in panicles to 6-12” long and female flowers in shorter racemose spikes). Female flowers produce three-parted capsule fruits with winged seeds. Edible conical bulbils (aerial tubers to 4” long) sometimes form in the leaf axils. Flowering, fruiting and bulbil production are uncommon in more temperate frost-free areas such as the southeastern U. S. Tubers for human consumption are usually harvested at the end of a single growing season. Unharvested tubers will increase in size from year to year with the potential of reaching gigantic dimensions over time (to 6-8’ long and to 100-150 pounds).

This vine is probably native to Southeastern Asia, but is known today only from cultivation. It has been suggested by some authorities that D. alata may be the result of a hybridization that took place several thousand years ago. This yam was first introduced into Florida by Spanish and Portuguese explorers in the 1500's. It has escaped cultivation and now persists in the wild (mostly to marshes, pond margins, drainage canals and waste areas) in the southeastern U. S. from Florida and Georgia along the Gulf Coast to Louisiana. This vine may grow as much as 6-8” per day in optimum conditions and can quickly blanket native vegetation including shrubs and tree crowns. It is today listed as a noxious weed by the State of Florida and a Category I Invasive Plant Species by the Florida Exotic Pest Plant Council (FLEPPC). Hundreds of cultivars exist worldwide, mostly varying in size, flesh color and texture.

Although some varieties of sweet potato (Ipomoea) are commonly called yams in the U.S. and Canada, sweet potato belongs to the morning glory family (Convolvulaceae) and is botanically unrelated to the true yams. From a culinary standpoint, however, true yams are considered to be a good potato substitute in hot climates where potatoes usually struggle.

Genus name honors Pedanios Dioscorides, first century Greek physician and herbalist.

Specific epithet from Latin means having wings in reference to the winged stems of this vine.

Common name of winged yam also is in reference to the winged stems.

Problems

No serious insect or disease problems. Anthracnose and viral diseases are occasional problems. Watch for aphids, scale and mealybugs. Nematodes may attack tubers.

Garden Uses

Vegetable gardens in frost free areas. Tubers may be eaten mashed, fried, boiled or roasted. Tubers may also be pounded to produce flour or starch. Interesting ornamental foliage plant for trellises, porches or pergolas. Container plant.